Mixing and dispersing device

ABSTRACT

A mixing and dispersing device in which an elongated shaft has connected thereto a rigid blade which undulates about a plane that is perpendicular to the shaft, to form a plurality of subblades a number of which are at a positive angle of attack and an equal number of which are at a negative angle of attack.

United States Patent Buck 1 51 July 25, 1972 541 MIXING AND DISPERSINGDEVICE 3,504,990 4/1970 Sugden ..416/l76 [72] Inventor: Barry L. Buck,414 N Lawndale 3,606,577 9/1971 Conn ..4l6/227 X Chicago, 60624 FOREIGNPATENTS OR APPLICATIONS 1 1 Filed= 25, 1971 1,144,900 4/1957 France..4l6/203 21 A L N J 113 742 1,297,805 5/1962 France ..4l6/l83 1 PP1,482,898 4/1967 France ..4l6/l83 250,542 1927 Great Britain ..416/183[52] US. Cl ..416/l83, 416/184, 416/223 [51] Int. Cl. ..B0lf 7/24Primary Examiner-Everette A. Powell, Jr. [58] Field of Search ..4l6/l83, 184, 185, I82, 181, Anomey-Lettvin and Gerstman [57] ABSTRACT 6 f [51 Re erences Cited A mixing and dispersing device in which an elongatedshaft UNITED STATES PATENTS has connected thereto a rigid blade whichundulates about a plane that is perpendicular to the shaft, to form aplurality of 1,745,441 2/1930 sub-blades a number of which are at apositive angle of attack 3,044,750 7/ 1952 and an equal number of whichare at a negative angle of at- 3,139,034 6/1964 tack. 3,244,410 4/19663,336,010 8/1967 4 Claims, 6 Drawing Figures PATENTED 3.679.323

INVENTOR BARRY L. B UCK BY m 4m, (1m

ATTORNEYS MIXING AND DISPERSING DEVICE FIELD OF THE INVENTION Thisinvention relates to an improved device for mixing and dispersing solidsand liquids, and more particularly, to a device in which a mixing bladehas a novel configuration.

BACKGROUND OF THE INVENTION Prior art mixing devices have variousdisadvantages. For example, mixing devices using simple propeller-typeblades are useful only for limited purposes. The propeller bladerotation causes a build-up of a relatively large vortex thereby causingair to enter the resulting mixture. Although such mixing action isuseful in the formation of milk shakes, whipped cream and other foodpreparations where the entry of air is desirable, such mixing action isdeleterious to mixing where air is not wanted.

Another type of prior art device which is widely used is the high-speeddisc impeller. This type of device generally gives relatively gooddispersement with little vortex formation. However, disc impellers donot afford good mixing except at high peripheral speeds and such highspeeds provide cavitation losses. Further, with disc impellers rotatingat high speeds, a relatively large amount of heat is generated. Thisrequires a time limit to the amount of mixing provided with a high-speeddisc impeller to prevent'the mix from overheating.

I have discovered a form of mixing and dispersing blade which providesstronger mixing action than is obtained with a propeller and can be usedat higher peripheral speeds without creating the large vortex that iscreated by propeller-type blades. At higher speeds, my novel bladeprovides much of the dispersive action that is generally obtained withthe highspeed disc impeller.

Other prior art devices have been tried to achieve various effects byshaping the mixing blade in a predetermined configuration and/or bymoving the blade in an unusual manner. For example, in U.S. Pat. No.189,469, issued to F. M. Johnson on Apr. 10, 1877, a mixing device isdisclosed in which the mixing blade comprises four paddles each of whichis separated from the other and is serpentine in configuration. Thepurpose of Johnsons blade is to convey air into the mixture by the upand down motion, and the device is used in a butter churn.

The patent to R. N. Ackles, U.S. Pat. No. 2,918,264, issued Dec. 22,1959, is an example of the type of device wherein the vortex is limitedby controlling the currents in the vicinity of vertical tips which areprovided on the mixing blade. This system eliminates radial materialtransfer to a large extent. On the other hand, my device permits theacceleration of material through substantially radially disposedchannels with the mix being forced strongly against the leading edge ofthe pitched section. There is strong but local turbulence, limitedmaterial transfer past the blades in order to limit the vortex, and ahigh exit velocity into the body of the mix or against the sides of thecontainer.

Accordingly, it is an object of my invention to provide a mixing anddispersing device for use where the entry of a large amount of air isimpermissible.

It is a further object of my invention to provide a mixing anddispersing device which provides strong mixing action at relatively lowspeeds with a reduced vortex and provides considerable dispersive actionat relatively high speeds without serious cavitation losses.

A further object of my invention is to provide a mixing and dispersingdevice having a novel configuration in which a rigid blade undulatesabout a plane that is perpendicular to the shaft carrying the bladethereon.

Other objects and advantages will be more apparent from the followingdescription and claims, and the illustrations in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a top plan view of a mixingand dispersing device in accordance with the principles of the presentinvention;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a side elevational view of a first modified form of theinvention;

FIG. 4 is a side elevational view of a second modified form of theinvention;

FIG. 5 is a side elevational view of a third modified form of theinvention; and

FIG. 6 is a side elevational view of a fourth modified form of theinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Referring to FIGS.1 and 2, it is seen that the device comprises a shaft 10 havingconnected thereto a blade 12 formed of eight sub-blades 14. Nolimitation is intended with respect to the number of sub-blades 14, asthere could be more or less than eight sub-blades, if desired.

Blade 12 is formed of a rigid material, such as steel, and isconfigurated so as to undulate about a plane a-a that is perpendicularto the axis of shaft 10. It can be seen from FIG. 2 that the portion ofblade 12 above perpendicular plane aa is symmetrical to the portion ofthe blade below the perpendicular plane.

In the embodiment of FIGS. 1 and 2, the blade is formed of a continuousfabrication and the undulations are substantially triangular incross-sectional configuration with the peaks and nadirs of eachundulation including an angle of The subblades 14 form a series ofradial channels which guide the material to be mixed radially outwardwith a tangential component resulting from rotation of the sub-blades,causing acceleration of the material against the positive faces of thesubblades.

Other configurations than triangular may be used successfully. Referringto FIG. 3, it is seen that the configuration is rectilinear incross-section with alternating sectors of the blade being successivelyhorizontal and vertical and joined at an angle of 90.

In FIG. 4, the blade has a sinusoidal cross-sectional configuration. Theembodiment of FIG. 5 is similar to the embodiment of FIG. 2, except thateach of the sub-blades 14 is separated from its adjacent sub-blades,with the separations 16 occurring at the peaks and nadirs of theundulations. It can be seen that sub-blades 14 are each formed of aseparate metal stamping and are fastened to the shaft 10 at the hubthereof.

The embodiment of FIG. 6 has a substantially sawtooth cross-sectionalconfiguration, but differs from the FIG. 3 embodiment because alternateportions 20 of sub-blades 14 extend in a vertical plane when shaft 10 isvertical, while intermediate portions 22 are disposed between alternateportions 20 and each include 45 angles at the peaks and nadirs of theundulations.

It can be seen that my mixing device includes a number of sub-blades ata negative angle of attack and an equal number of sub-blades at npositive angle of attack, with one set of subblades providing working ofthe material and the other set of sub-blades providing guidance of thematerial. Material feed is limited to eliminate the vortex radial to theshaft and resulting mixture of air.

The blades are arranged in such a way that the material being mixedundergoes successive impact impingement, shear and reentry into acondition to repeat these processes on a successive blade, this reentrybeing by flow into the space voided by the first blade. The deviceutilizes the inertia of a fluid which may be too thin to allowdispersion by shear and approximates a shear effect by briefly andviolently accelerating the material over and over against the bladesurface and at the same time severely restricting the amount of materialtransferred past the device. Because of the unique construction of myblade, good mixing and dispersion can be obtained at relatively low rimspeeds, such as 1,000 feet per minute, in contrast to a speed of morethan 3,000 feet per minute needed with prior art blades.

Although illustrative embodiments of the invention have been shown anddescribed, it is to be understood that various modifications andsubstitutions may be made by those skilled in the art without departingfrom the novel spirit and scope of the present invention.

WHAT IS CLAIMED IS:

1. A mixing and dispersing device which comprises: an elongated shaftfor connection to a drive means, said shaft having connected thereto arigid blade comprising a plurality of subblades, said rigid blade beingsymmetrical about a plane that is perpendicular to said shaft andintersects said blade, each of said sub-blades having a planar surfaceand forming a triangular configuration with its adjacent blade, saidsub-blades extending outwardly from the shaft with the vertices of thetriangles being free from contact with any supporting means.

2. A mixing and dispersing device as described in claim 1, wherein theincluded angle of each triangle is about 3. A mixing and dispersingdevice as described in claim 1, wherein the included angle of eachtriangle is about 45 and each alternate sub-blade extends parallel tothe axis of the shaft.

4. A mixing and dispersing device as described in claim 1, wherein eachsub-blade is separated from its adjacent subblades, with the separationsoccurring at the corners of the triangles.

1. A mixing and dispersing device which comprises: an elongated shaftfor connection to a drive means, said shaft having connected thereto arigid blade comprising a plurality of subblades, said rigid blade beingsymmetrical about a plane that is perpendicular to said shaft andintersects said blade, each of said sub-blades having a planar surfaceand forming a triangular configuration with its adjacent blade, saidsub-blades extending outwardly from the shaft with the vertices of thetriangles being free from contact with any supporting means.
 2. A mixingand dispersing device as described in claim 1, wherein the includedangle of each triangle is about 90* .
 3. A mixing and dispersing deviceas described in claim 1, wherein the included angle of each triangle isabout 45* and each alternate sub-blade extends parallel to the axis ofthe shaft.
 4. A mixing and dispersing device as described in claim 1,wherein each sub-blade is separated from its adjacent sub-blades, withthe separations occurring at the corners of the triangles.